Showing results for 
Search instead for 
Did you mean: 
What's DOS?
Posts: 2
Location: Planet Earth
Views: 3,234
Message 1 of 5

Is my integrated camera OK? - Thinkpad T420

The integrated camera on my Lenovo T420 behaves very strangely under Linux. In daytime, the image is badly overexposed, nearly white. It looks like automatic exposure adjusment does not work. Even if i switch to the manual mode I cannot reduce exposure level below 333. I run Ubuntu 11.04 32bit (kernel t2.6.38-13-generic-pae), but also tried Scientific Linux 6.1 and several Linux Live CDs, and the problem persists.


The camera worked fine until I tried skype using Mint 12 Live CD. It was then that the image suddenly turned black during the call, and since then I have this problem with overexposure. 


Under Windows Enterprise 64bit, right after I reboot from Linux, the image is badly overxposed too. However pressing Fn+F6 and going into advanced settings restores the image quality, and I can see that the exposure level changes as I move from the window to a darker corner. When I reboot back to linux, the correct image splashes for a fraction of a second, and then the overexposed image shows on the screen again.

Do you think, is this a hardware problem which Windows driver knows how to deal with, while the Linux driver does not? The laptop is under warranty, so should I have Lenovo involved?

What's DOS?
Posts: 1
Location: chennai, india
Views: 3,151
Message 2 of 5

Re: Is my integrated camera OK? - Thinkpad T420

Hi, I am also having the same problem. I am using Ubuntu 11.10 64bit, I have a installed windows xp as a virtual machine. It is also having the same issue.
Retired Moderator
Retired Moderator
Posts: 2,933
Location: US
Views: 3,148
Message 3 of 5

Re: Is my integrated camera OK? - Thinkpad T420

To the OP 


I am not sure if Lenovo would help if you want some help regarding the camera in Linux,how ever,If you have a problem with it while you are using windows,they would help  IMO (Because your system came pre-installed with windows) 

What's DOS?
Posts: 2
Location: Planet Earth
Views: 3,121
Message 4 of 5

Re: Is my integrated camera OK? - Thinkpad T420

In fact, I don't have preinstalled OS anymore. Our IT department replaced the preinstalled Win 7 Home Premium with Win 7 Enterprise. Am I out of luck?
Paper Tape
Posts: 7
Location: Belgium
Views: 2,494
Message 5 of 5

Re: Is my integrated camera OK? - Thinkpad T420

I have the same problem, and at least I have found a workaround. I don't know if the issue is still relevant for you but here it goes:


- Install a tool like v4l2ucp (sudo apt-get install v4l2ucp) and start it

- I assume the setting of "Power Line Frequency" is "60 Hz" (this is the default)

- While a webcam application is running, set the setting to "Disabled": Exposure should be okay


The problem that remains is, that if you close the webcam application, and start it again, the image is again overexposed, while the setting is still on "Disabled". So you need to first change it to "60 Hz" and then again to "Disabled".


I'm trying to contact the v4l2 and UVC developers to see what they say about this. Maybe a solution could be a patch, that sets the default of "Power Line Frequency" to "Disabled".





Top Kudoed Authors